Lecture 16: Taste, Smell, Touch

how do we differentiate between the 2 chemical senses?

depends on the avenue taken to the brain

what nerve is odor information transmitted down?

on the 1st cranial nerve to rostral part of brain, telencephalon of frontal lobe

(olfactory CN1)

where does gustatory information go?

cranial nerves 7, 9, 10 to the middle/back of brain

what are the 3 types of 4 cells in a taste bud?

attached to oral cavity and through the taste core:

1 and 2: supporting cells

3: taste cell (center, receptor cell)

4: stem cell, produces more taste cells

info to the brain

what is cranial nerve 10 attached to?

back of throat, vagus

what is cranial nerve 9 attached to?

glossopharyngeal

what is cranial nerve 7 attached to

facial nerve, arises from the brain stem and extends posteriorly to the abducens nerve and anteriorly to the vestibulocochlear nerve

what is the pathway of taste to the brain?

taste cell >> gustatory sensory neuron >> sensory ganglia >> CN 7 9 10 >> brainstem medulla, Nucleus of Solitary Tract >> thalamus >> gustatory cortex in parietal lobe

what are salty and sour tastes mediated by?

ionotropic receptors, directly activate depolarization

what are sweet, bitter, and umami tastes mediated by?

metabotropic receptors, have g-protein coupled receptors that act as second messengers once taste chemical attaches to outside cell

what is important to remember about taste cells?

they are not neurons, but are still electrochemically active

Where is the olfactory bulb located?

under ventral part of frontal lobe

what does a glomeruli collect in the olfactory bulb?

1 odorant sorted by thousands of olfactory receptor neurons

what is the pathway of scent to the brain?

nasal cavity >> epithelium mucus surface >> olfactory receptor neuron >> olfactory bulb >> glomeruli >> cranial nerve 1 >> entorhinal cortex (hippocampus), piriform cortex (frontal lobe), amygdala, hypothalamus

what does anosmia mean?

loss of smell

what does ageusia mean?

loss of taste

Which system is where most of our stem cells are as an adult?

olfactory

Nocioreceptors are sensory neurons that respond to:

pain, they are a type of exteroreceptor

true/false: the olfactory system contains more types of receptors than the gustatory system.

true

What do mechanoreceptors respond to?

touch, pressure, vibration, stretch

what do interoreceptors provide information about?

state inside body, mostly in the gut

What do proprioceptors do?

monitor the position and movement of skeletal muscles and joints

muscle spindles and golgi tenden organs

what is the pathway of discriminative touch?

ipsilaterally up the spinal cord, cross at brainstem medulla

what is the pathway of pain, temperature, and tickling? (anterolateral system)

contralaterally up the spinal cord, different sides help identify lesions on spinal cord